This report examines how FHWA’s investment in roundabout research affected the availability and quality of such research, the adoption of roundabouts in the United States, and the impacts of those roundabouts on safety, operational, and environmental performance of the U.S. transportation system.

The findings of this report should be of interest to engineers, practitioners, researchers, and decision makers involved with the research, design, performance, and management of roundabouts and other alternative intersection designs.